Abstract
This paper reviews recent efforts, mostly at the author's laboratory, to relate liquid and semi-solid texture to rheological and frictional properties and to relate texture-taste interactions to diffusion coefficients.
First, the large texture vocabulary is reduced to a few key attributes of ‘thick’, ‘smooth’ and ‘slippery’ using statistical analysis. A model is presented approximating the deformation process and capable of predicting shear stress in the mouth, which is solved for Newtonian, ‘non-Newtonian’ and ‘non-Newtonian foods with time dependent rheology’. Shear stress is then related to magnitude estimation of ‘thickness’. Similar approaches lead to prediction of ‘spreadability’ using a knife.
‘Smoothness’ is shown to be related to the inverse of the friction force required to have skin slip across skin or food, and ‘slipperiness’ is shown to be related to the inverse of the sum of viscous and frictional forces. ‘Creaminess’ is shown to be predicted from scores of ‘thickness’ and ‘smoothness’.
Viscosity-taste interactions are explained by assuming that the rate of diffusion of tasting agent to the surface of the tongue is slower than the rate of the taste reaction responsible for the intensity of a tasting reaction. Therefore, the ‘flux’ of tasting agent controls the rate of the tasting reaction. The penetration model of mass transfer suggests that this flux is proportional to the square root of the diffusion coefficient. This concept is shown to explain viscosity-taste interactions.